Quantum cryptography based on fundmental physical principles has been proved to be an effective technique for secure key distribution.The fundamental theory of quantum cryptography together with their main schemes and protocols is discussed in this paper. Recent improvements of quantum cryptographic communication are analyzed, and the existing problems and development prospect in future are also pointed out.

Liquid core optical fibers can provide very high detectable sensitivity for Raman spectra measurements of liquid samples. Raman spectra by use of liquid core optical fibers and their development are introduced and described. The characteristics and developments of liquid core optical fibers, main intensity considerations in liquid core optical fiber Raman spectroscopy and excitation/collection geometries, and photobleaching and efficient elimination of fluorescence background in liquid core optical fiber Raman spectroscopy are detailedly analysed. The main applications of liquid core optical fibers are especially described in detail. It is of important reference value to the study on Raman spectra measurements of liquid samples using liquid core optical fibers.

The time-dependent Schrodinger equation governing the time-dependent weakly coupling Bosonic gas is exactly solved by use of the Lewis-Riesenfeld invariant theory in the present paper. This enables us to treat the time evolution of the Bosonic gas. Since the Bogoliubov transformation formulation in the time-dependent case may yield a phase factor that cannot be determined by the theory itself, we calculate the transformation coefficients between the Bosonic occupation representation and the quasi-particle representation and, based on this, obtain the complete set of vector basis of the quasi-particle representation for the time-dependent weakly coupling Bosonic gas.

By the aid of the linear quantum transformation theory, we derive the analytic expression of the partition function for the quadratic systems. With this formula, we can obtain the partition function of the systems without any information for the energy spectrum.

The characteristics of Cr4+, Nd3+:YAG are presented. A self-Q-switched Cr4+, Nd3+:YAG laser pumped by fiber-coupled diode laser produces 1064 nm pulse laser with the average power of 3.36 W, the pulse duration of 65 ns, and the repetition rate of 87 kHz. The opto-optical efficiency is 15.3%. When the KTP crystal is inserted into the cavity, the 532 nm green pulse laser is obtained. The average output power is 1 W, the pulse duration is 210 ns, the repetition rate is 47 kHz, and opto-optical efficiency is 6%.

Numerical modeling has been given to describe the relation between optimal crystal length and the transmission of 946 nm output. The equation had been derived of the laser rate formula of the steady-state case in the laser cavity. By comparison of the output transmission between 946 nm and 1064 nm, we give a series of diagrams which discribe the minimized claims to coat in many cases. How the concerned factors influence the 946 nm lasing threshold and its output power has also been given. All the results will be useful for more efficient operation at 946 nm of Nd:YAG. The metholds adopted to deal with the low gain and quasi-three-lever or three-lever system will be enlightening.

A study on a tunable fiber laser is presented in this paper. A twenty-meter-long double-cladding Yb3+-doped fiber laser which tuning range is 42 nm in Littman configuration and line width is less than 0.06 nm is pumped by a high-power multimode LD system. The output power is up to 460 mW, and the slope efficiency is about 30%. The optimization of high-power tunable fiber lasers is discussed.

Self-pulsation behavior of Yb3+-doped double clad fiber lasers formed in Fabry-Perot cavities and end-pumped by CW laser diode (LD) is investigated. Two kinds of self-pulsation are observed in the fiber laser with a low Q cavity, one is the pulse generated from passive Q-switching of saturable absorption;the other is the giant pulse due to stimulated Raman scattering (SRS) in the fiber. It is demonstrated that by promoting the Q value of the cavity the pulsation in the output of the fiber laser can be reduced and stable CW output will be obtained while an appropriate rate of pump is applied simultaneously.

By means of a microwave generator chlorine diluted by helium was dissociated to chlorine atoms which subsequently reacted with hydrogen azide to produce the excited states of NCl(a1△) and NCl(b1∑). In this paper, the intensity of NCl(a1 △) and NCl(b1∑) emissions dependent on the flow rates of different gases is studied. The results are presented and discussed.

The temperature greatly influences the characteristics of laser diode. If a stable output wavelength is required, the temperature of the laser diode must be maintained a constant level. In this paper, we use the operation amplifier with high S/N, a normal temperature sensor with negative temperature modulus, and a semiconductor cooler as temperature control instrument, and we succeed in inventing a high precision temperature instrument which is used in the semiconductor diode temperature control, the precision of the controlled temperature is ±0.03℃.

Numerical computation and numerical reconstruction of optical fields distribution are investigated in this paper. The formula of numerical computing is presented with discretion for Fresnel diffraction and phase numerical reconstruction of wave front. For example, light propagation through an aperture and numerical reconstruction of digitally stored holograms. The result shows that it exhibits obviously optical character with numerical computing, which provides visual validation for optics.

We realized closed loop control system of BBO optical parametric oscillation tuning system, by using American General Scanning Inc.'s controller to control BBO crystal's rotation, and demarcated the output wavelength with charge coupled device (CCD). The system's relative wavelength tuning error was less than 0.04%. We also demonstrated 0.347 μm pumped type Ⅰ phase matching BBO optical parametric oscillation's theoretical and experimental curve of output wavelength versus pumped light incidence angle.

This paper is concerned with the synchronization of chaotic systems. We discuss the synchronization using parametric adaptive control algorithm to adjust one of the parameters of the response system with the appropriate controlling law and controlling coefficient. To make this method realizable, the Logistic mapping and Henon mapping are taken as two typical numerical examples. Both the theoretical and numerical results seem to suggest that synchronization error will gradually be zero under the assured controlling law and controlling coefficient in which chaos synchronization will be achieved.

The effects of photon antibunching in the interaction of a cascade three-level moving atom with single-mode field are studied. The influences of atomic motion, the field structure and intensity on the photon antibunching are discussed.

A two-level atom is put in noise field, which is described as thermal reservoir. The interaction of atom with noise field is considered. The non-opposite angle element of two-level atom's reducible density mafvix is obtained and decoherence of two-level atom is studied. We discuss atom's decoherence through an external controllable driving field. And the properties of an external driving field are obtained when atom's coherence is maintained.

According to the characteristic of gas molecule absorbability in infrared light, remote measurement of vehicles emission CO and CO2 by non-dispersion infrared was investigated in this paper. By using single IR detector, CO,CO2 and background were measured. The combination of gas filter and lock-in-amplifier were used to detect the week signal. Many shortcomings of conventional method were conquered, such as low precision of detection and the detection of vehicles which under real-world driving condition. The relation of gas concentration and signal under immobile condition was also described. The mobile condition results show that the emission from vehicles which under real-world driving condition can be measured online automatically.

The article described the process of photons' movement in tissue by using the principles of tissue optics to measure the thickness of fat. Based on the established mathematical model of photons' movement, we confirmed the direction of photons' movement, position and the change of weight, and obtained the final analytic result. At the same time, we could acquire a part of simulative result based on the analytic result. The accordance of measurement and the way of test were studied primarily.

In this paper, we introduced the super-bright blue-purple light emitting diode (LED) into a novelty light resource which excited chlorophyll-a to emit fluorescence. Furthermore, we compared LED with the ordinary excitation resource. By two experiment apparatus, we have measured the fluorescence signal and obtained the chlorophyll-a fluorescence emission spectra. The results show that LED can act as an alternative excitation resource in developing the fluorometer for the in situ measurement of the chlorophyll-a concentration in water.

This paper introduces the study of mine hoister tracking system based on infra-red laser orientation technique, the application of dual-port RAM in the distance measurement system of mine hoister and gives an operation theory of dual-port RAM IDT7132. According to its different operation modes, the hardware arbitration and software arbitration are presented, and the flow chart of data exchange with IDT7132 is given. This measure has no transmission error and no need of assistant correcting switch. At the same time, it can show the actual location of mine hoister to realize controlling the digitized speed of the hoister

Based on the analytical solutions of a double clad (W-type) chiral optical fiber, the effects of chirality and thickness of inner cladding on the mode dispersion have been studied by numerical method. Effects of chirality and thickness of inner cladding on the normalized phase constant b, group delay d(Vb)/dV and waveguide dispersion Vd2(Vb)/dV2 as functions of the normalized frequency V for the fundamental mode of double clad chiral optical fibers are presented. The results demonstrate that by introducing chirality to the core, inner and outer cladding of an optical fiber can change its mode dispersion characteristics drastically. The dispersion characteristics are very different for different thickness of inner cladding.

The properties of the soliton propagation and coupling in fiber communication are analyzed by using the coupling model of equivalent twin wave-guides soliton and self-companying operator method. The method of removing fission and deformation of the optical solitons by using the stationary spasm laser in the pulse hole in nonlinear optical dielectric has been given.

With an effective two-site Hubbard model, the dynamic behaviors of an exciton confined in coupled double quantum dot system driven by high AC field are investigated. Solving the Floquet equation by the perpeturbation theory, we obtain the analytical solution of quasi-energies. The calculation shows that the quasi-energy levels versus the amplitude of external field can develop into a series of resonance point. Calculating the time evolution of the initial states, we find the initial localized state can hold on forever at the resonance point. This demonstrates that it is possible to control the entangled states on extremely short timescales using the appropriate AC field with the adjustable amplitude and frequency, which may be useful for quantum information processing.

An imaging system based on MCP (MicroChannel plate) detector is designed to image the extreme ultraviolet (EUV) light at 30.4 nm. The image of a 3 mm-width-slit is obtained by this imaging system. Its spatial resolution of 490 μm is demonstrated. Moreover, all kinds of factors influencing the resolution of the imaging system and the measures to improve the resolution are analyzed in this paper.

Based on the theory of degenerate two-wave mixing, a method to determine both the gain coefficient and absorption coefficient of photorefrative crystals is presented. Using this method we have measured the Γ and a of a sample crystal Ce:KNSBN.

A method for analyzing cross-section intensity distribution of laser beam by digit technology is introduced in this article. With this method, an experimental device was set up. The hardware of this system was composed of optical preprocessing unit. CCD detector, video card and computer. With the analytic software, the mathematical function, curve and 3D picture about cross-section intensity distribution of laser beam and fitting analysis with Gaussian function were realized.